title: ATR-IR spectroscopic study of L-lysine adsorption on amorphous silica.
abstract: Attenuated total reflectance infrared (ATR-IR) spectroscopy was employed to quantitatively evaluate the dissociation states (di-cationic, cationic, zwitterionic, and anionic) of lysine adsorbed on amorphous silica. To determine the relationship between the ATR-IR spectra and each dissociation state, we first measured pH-induced spectral changes of dissolved lysine and correlated these changes with the thermodynamically calculated dissociation states of lysine. This procedure yielded calibration curves with good linearity; we used these curves for the quantitative analysis of adsorbed lysine. Our analysis revealed that 81+/-5% of the lysine adsorbed on amorphous silica was present in a cationic state and 19+/-5% was in a zwitterionic state; these percentages remained mostly unchanged over the whole range of pH values tested (pH = 7.1-9.8). We interpret the values obtained to indicate that lysine adsorption is mainly driven by electrostatic interaction with the negatively charged silica surface (SiO(-)...Lys(+), SiO(-)...Lys(+/-)).
authors.affiliation: Department of Earth and Space Science, Graduate School of Science, Osaka University, 1-1 Machikaneyama, Toyonaka, Osaka 560-0043, Japan. nkitadai@ess.sci.osaka-u.ac.jp
authors.forename: Norio
authors.initials: N
authors.lastname: Kitadai
authors.forename: Tadashi
authors.initials: T
authors.lastname: Yokoyama
authors.forename: Satoru
authors.initials: S
authors.lastname: Nakashima
mesh_terms: D000327:Adsorption; D002138:Calibration; D006863:Hydrogen-Ion Concentration; D008239:Lysine / Q000737:chemistry*; D012822:Silicon Dioxide / Q000737:chemistry*; D013055:Spectrophotometry, Infrared; D013499:Surface Properties
chemical_list: D012822:Silicon Dioxide; D008239:Lysine